Most personal care products on the market contain many types of polymers that vary by structure, chemistry, and raw material source (synthetic or natural) that are combined to provide products with many different desired functions. One class of polymer additives is targeted at altering or modifying the rheological properties of the product that are very important for consumer appeal. Often, additives that provide sufficient viscosity are needed, especially for those formulations where the viscosity without additives is close to that of the pure solvent (water). However, merely increasing viscosity is not sufficient, and in reality, the modifiers should be selected to provide certain desired rheological properties for the formulation that depend on its nature, the mode of delivery, type of flow, and the aesthetic appeal of final application. Typically, low molecular weight surfactants are used to modify rheological properties but they have to be used at large concentrations. Resulting in relatively high cost, and an adverse impact on the environment (e.g., water pollution).
The thickeners used in cosmetic and body care preparations have to meet stringent requirements. First and foremost, they have to show high compatibility and also—if possible—biodegradability so that many substances have to be ruled out from the outset for use in cosmetics. In addition, they should be universally useable in aqueous, emulsoidal, alcoholic and oil-containing bases, be readily processable and lead to a rheology which enables the product to be easily applied so that the preparations can be removed and distributed under clean and simple conditions.
Thickeners that are designed molecular level to provide the desired properties would be expected to be compatible with many other auxiliaries, more particularly with salts and surfactants. The thickener itself and the other auxiliaries should also lend themselves to ready incorporation into the formulation. The thickened preparations are also expected to show stable rheology and an unchanging physical and chemical quality even in the event of long-term storage and changes in pH and temperature. Finally, the thickeners should be inexpensive to produce without causing significant environmental pollution.
In view of this complex requirement profile, it is clear why, even today, there is still a demand for new thickeners in the cosmetics field.